This invention relates to scaffolds. More specifically, this invention relates to a hoistable, rotatable scaffold for use in gaining access to the inside wall of an upright, variable diameter cylindrical tank.
Upright cylindrical tanks are widely used throughout industry and are particularly valuable in oil refining processes where they are used as catalytic reactor towers. Typically, such reactor towers have a height of up to about two hundred feet, and a diameter varying between about 20 feet and 40 feet over the tank height. Such tanks are formed from steel or the like, and are used in distilling various liquids at various elevations thereof. Such distilled liquids run down the inside wall of the tank for collection, and this causes a slag formation on the inside tank wall over a period of time. This slag build-up is usually more severe toward the top of the tank, and is highly detrimental to the refining process. Accordingly, the reactor tank must be shut down, or removed from production, once or twice each year to allow the slag deposits on the inside wall of the tank to be removed.
According to conventional practice, a small manhole having a diameter of about thirty inches is provided near the bottom of a refinery reactor tank to allow access inside. When the tank is shut down for maintenance, the manhole is opened and scaffolding material is passed therethrough. Inside the tank, a conventional tubing and plank scaffold is constructed from the floor all the way to the top, and in close proximity with the inside tank wall. Construction of the scaffold, however, is a difficult and time-consuming task because of the tight working conditions inside the tank as well as the varying tank diameter. Thus, scaffold construction can take up to several working days to complete. This is highly undesirable in the refining industry wherein an idle reactor tank can result in losses of substantial revenue each day.
Once the scaffold is constructed within the tank, it is common practice for workers to clean the inside wall of the tank beginning at the top and moving downwardly toward the bottom. In this manner, all of the inside tank wall is reached, with the scaffold being gradually dismantled as the work progresses. However, such dismantling is also a time-consuming task to thereby further prolong the time the reactor tank is idle. Further, slag chunks weighing as much as 100 pounds can become dislodged from the tank wall during cleaning, and such chunks can fall against and damage the scaffold below the workers to endanger the scaffold stability.
The scaffold of this invention overcomes all of the disadvantages and problems of conventional tubing and plank scaffolds used in the prior art by providing a scaffold which is quickly and easily assembled and disassembled within a reactor tank. Further, the scaffold of this invention is supported from above and is vertically movable to any elevation within the tank. Moreover, the scaffold of this invention is diametrically adjustable and rotatable within the tank to allow workers easy access to any portion of the tank inside wall.